A 67-year-old man has recurrent witnessed episodes of loss of consciousness while shaving. The episodes are characterized by a feeling of faintness followed by loss of consciousness, and each episode resolves after less than a minute. Blood pressure is 130/80 mm Hg and pulse is 80/min and regular; there are no significant changes in blood pressure or heart rate with supine and standing positions. Cardiac auscultation is normal with no murmurs or extra sounds. There are no neck bruits and the lungs are clear to auscultation. Which of the following factors is most likely contributing to this patient's symptomatic episodes?

Question

A 67-year-old man has recurrent witnessed episodes of loss of consciousness while shaving.  The episodes are characterized by a feeling of faintness followed by loss of consciousness, and each episode resolves after less than a minute.  Blood pressure is 130/80 mm Hg and pulse is 80/min and regular; there are no significant changes in blood pressure or heart rate with supine and standing positions.  Cardiac auscultation is normal with no murmurs or extra sounds.  There are no neck bruits and the lungs are clear to auscultation.  Which of the following factors is most likely contributing to this patient's symptomatic episodes?

Quizplus · Accepted Answer

11ec160b_3a82_bad0_9249_5dbbc13b9354_MD0001_00 This patient with recurrent episodes of syncope while shaving most likely has carotid sinus hypersensitivity (CSH). When carotid sinus baroreceptors detect increased blood pressure, the brainstem responds by increasing parasympathetic tone (slows the heart rate) and reducing sympathetic tone (induces vasodilation). In some individuals, especially elderly men, the carotid sinus baroreceptors become overly sensitive to tactile stimulation, triggering an exaggerated vasovagal response with marked peripheral vasodilation (ie, decreased systemic vascular resistance). This can cause a transient reduction in cerebral perfusion that manifests as presyncope (eg, faintness, lightheadedness) or syncope. As with other etiologies of syncope, cerebral perfusion quickly returns and symptoms resolve within 1-2 minutes. In addition to shaving, rubbing of a shirt collar while dressing or turning the head is another common cause of syncope due to CSH. (Choices A and E) Cardiac tachyarrhythmias are a serious cause of syncope due to reduced cardiac output and loss of cerebral perfusion. Spontaneous resolution of the arrhythmia within 1-2 minutes allows for return of cerebral perfusion (if spontaneous resolution does not occur, the arrhythmia may cause sudden death rather than syncope). Atrioventricular nodal reentrant tachycardia rarely causes syncope as it usually affects young patients who can tolerate rapid heart rates. Polymorphic ventricular tachycardia (torsade de pointes) typically results from delayed ventricular repolarization (ie, congenital or medication-induced QT interval prolongation) and can cause syncope in patients of any age. Syncope due to tachyarrhythmia usually occurs suddenly with no warning symptoms (eg, faintness, lightheadedness) other than sometimes palpitations. (Choice C) Acute pulmonary embolism (PE) obstructs pulmonary blood flow and increases pulmonary vascular resistance. Some cases of acute PE present with syncope, but acute PE is unlikely to explain recurrent episodes of syncope. In addition, chronic pulmonary hypertension typically presents with exertional symptoms. (Choice D) The exaggerated vagal response in reflex syncope causes transient sinus bradycardia, PR interval prolongation, and atrioventricular (AV) node conduction block, whereas syncope due to age-related degeneration of the AV node usually involves sustained and advanced AV block (eg, third-degree, Mobitz type II second-degree). This patient's recurrent episodes during shaving make reflex syncope due to CSH more likely. Educational objective: Carotid sinus hypersensitivity is a common cause of syncope associated with tactile stimulation of the carotid sinus (eg, shaving). The syncope results from an exaggerated vagal response stimulated by the carotid baroreceptors, which leads to slowed heart rate and marked peripheral vasodilation with a resulting transient loss of cerebral perfusion. __________ References: Carotid sinus syndrome: progress in understanding and management. (http://www.ncbi.nlm.nih.gov/pubmed/25405171)

A 67-Year-Old Man Has Recurrent Witnessed Episodes of Loss of Consciousness